In 1988, NIMH & NIDA funded the AMEN cohort survey as part of an AIDS center grant to the Center for AIDS Prevention Studies. This survey collected two waves of behavioral and serological on 1,423 unmarried (at baseline) respondents residing within San Francisco, age 20-44, with approximately equal representation by black, Hispanic, and white populations. The proposed study will extend this work to obtain two more waves of behavioral and psychosocial data. This longitudinal study will examine respondents changes in sexual behavior, HIV test-seeking, HIV-related beliefs, and intravenous drug use practices over a one year period. We will also provide a rigorous test of the AIDS Risk Reduction Model (ARRM, Catania et al., 1990) and generate data on patterns of sexual mixing across social strata. The findings will (a) aid in identifying segments of the population (defined by race/ethnicity, gender, marital status, age, social class) who continue to perform high risk activities, and therefore, are in need of intervention, (c) provide data relevant to intervention content development, (d) provide a rigorous longitudinal test of the ARRM, and (e) generate findings of import to questions of population spread of HIV (sexual mixing). The findings will be of fundamental importance to the development of HIV prevention programs and policy.